Memory tags in the form of Radio Frequency Identification (RFID) tags are well known in the prior art. RFID tags come in many forms but all comprise an integrated circuit on which, in use, data can be stored, and a coil that enables it to be interrogated by a reader that also powers it by means of an inductive (wireless) link. Generally RFID tags are quite large, due to the frequency they operate at (13.56 MHz) and the size of coil they thus require, and operate over large ranges and have very small storage capacities. Smaller RFID tags have also been developed, operating at various frequencies, but still having small storage capacities. Some RFID tags include Read Only Memory (ROM) and are written to at the time of manufacture, whilst others have read and write capability. RFID tags have tended to be used in quite simple applications, such as for file tracking within offices or in place of or in addition to bar codes for product identification and supply chain management.
One use to which such RFID tags can be put is the annotation of items, such as documents, with data over and above that printed on them. For example, in EP 1 076 316 A2, Eastman Kodak Company describe the use of an RFID tag of conventional form secured to a print, being an output image on a substrate, possibly of a photograph. The kind of data which it is envisaged will be stored in the RFID tag on the print relates to the manner in which the print has been processed, particularly if the print is an output sheet from a proofing system. In any event the examples of data given range from 8 bits to 256 bits. A technique is described for communicating with multiple prints within range of the transceiver used to communicate with them, such as for example if a single print needs to be located amongst a file of such prints.
GB 2395592, discloses the annotation of objects, such as documents, with electronic data. In this document, one or more memory tags are arranged in or on the object which is to be annotated.
A significant disadvantage with such annotation is that the data stored in a memory tag is accessible by a reader, which powers up the tag and causes its stored information to be output. This is particularly undesirable when the data that is stored is of a sensitive or confidential nature. An example of such data are the medical details of a patient annotated to that patient's medical card. It is problematic that any person with access to a reader may access this information by bringing that reader into close proximity with the memory tag whether or not they are authorised to do so. Hence, it is desirable to secure access to memory tags that are used to annotate items.
Currently, security may be provided by the provision of security measures in the two way exchange between a memory tag and reader. For example, the reader may require the entry of a password or code to activate it prior to its use. However, to ensure a reasonable level of security, a password or code must be of a sufficient length or complexity to prevent it being easily determined by trial and error. This presents a problem to the user of the reader in that memorising the given password or code may be difficult. People are required to memorise many passwords and codes for security purposes including, for example, computer network passwords and bank and/or credit card personal identification numbers. The longer a password or code is and/or the more passwords or codes that must be renumbered, the greater the likelihood is that a user will be unable to recall the necessary password or code. This often leads to users writing down codes as an aide memoir. Such aides memoir may be observed/obtained by third parties, and may therefore be a major source of security violation.